// Copyright 2019 Yan Yan
// 
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// 
//     http://www.apache.org/licenses/LICENSE-2.0
// 
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include <spconv/reordering.h>
#include <torch/script.h>
#include <ATen/Parallel.h>

namespace spconv {
namespace functor {
template <typename T, typename Index>
struct SparseGatherFunctor<tv::CPU, T, Index> {
  void operator()(const tv::CPU& d, tv::TensorView<T> buffer, tv::TensorView<const T> features,
                  tv::TensorView<const Index> indices, int size) {
    int numPlanes = features.dim(1);
    at::parallel_for(0, size, 0, [&](int64_t begin, int64_t end){
      for (int i = begin; i < end; ++i) {
        std::memcpy(buffer.data() + i * numPlanes,
                    features.data() + indices[i] * numPlanes,
                    sizeof(T) * numPlanes);
      }
    });
  }
};

template <typename T, typename Index>
struct SparseScatterAddFunctor<tv::CPU, T, Index> {
  void operator()(const tv::CPU& d, tv::TensorView<T> outFeatures,
                  tv::TensorView<const T> buffer, tv::TensorView<const Index> indices,
                  int size, bool stable) {
    int numPlanes = outFeatures.dim(1);
    const T* buf = buffer.data();
    T* out = outFeatures.data();
    for (int i = 0; i < size; ++i) {
      buf = buffer.data() + i * numPlanes;
      out = outFeatures.data() + indices[i] * numPlanes;
      for (int j = 0; j < numPlanes; ++j){
        out[j] += buf[j];
      }
    }
  }
};

} // namespace functor


#define DECLARE_CPU_SPECS_T_INDEX(T, Index)               \
  template struct functor::SparseGatherFunctor<tv::CPU, T, Index>;  \
  template struct functor::SparseScatterAddFunctor<tv::CPU, T, Index>;

#define DECLARE_CPU_SPECS(T)                                                   \
  DECLARE_CPU_SPECS_T_INDEX(T, int);                                           \
  DECLARE_CPU_SPECS_T_INDEX(T, long);

DECLARE_CPU_SPECS(float);
DECLARE_CPU_SPECS(double);
DECLARE_CPU_SPECS(at::Half);

#undef DECLARE_CPU_SPECS
#undef DECLARE_CPU_SPECS_T_INDEX

} // namespace spconv

